Do I have to create a custom control as lookless?

Question

I am creating a custom control derived from the one of the Standard WPF controls. The control has several constituent parts,and I am only modifying one of those parts.

Here's my question: If I am modifying only one part of a control, do I have to declare the control as lookless and reproduce the entire control template for the modified control in Generic.xaml, or can I omit the lookless declaration (found in the static constructor provided by Visual Studio) and simply modify the control template for the part I am extending?

I have tried the latter approach, and my control template is being ignored. I would like to get confirmation before I reproduce the entire control template, since what I am extending is the WPF Calendar. Thanks for your help.

Answer 1

Hi David

It sounds like your best bet is to paste the entire template and modify the parts you need, although you didn't say exactly what you want to do or post any code.

Obviously if what you want to change about the calendar has a property you can modify in xaml, then that is easier. The opposite extreme would be to create a custom control (subclass).

I wanted to change the color or the ComboBox arrow the other day and the easiest way to do that was to past the entire template into a style and apply as needed, after changing one single part of the template (the arrow color, of course). There is no exposed DP to change for this and I didn't need anything more complicated than that.

HTH,
Berryl

Answer 2

The declaration that's generated for you by default is simply allowing for a default implicit Style to be defined for your control instead of just taking on the default Style of the base type.

DefaultStyleKeyProperty.OverrideMetadata(typeof(MyControl), new FrameworkPropertyMetadata(typeof(MyControl)));

What makes a control lookless isn't any specific declaration but rather it's definition in a code file which will then have some ControlTemplate applied to it at runtime. The alternative is the UserControl style of declaring a XAML+code-behind class which compiles into a single class with both UI and logic.

A simple example: Button is not the thing you see on the screen and click on; Button is a control that can take a single piece of Content and translate a user click into a Click event or Command call. What you see on the screen is just a visual template on top of Button's inherent behavior and state.